Devices for dispensing an active volatile liquid in the surrounding space have been known for a long time. One type device is the so-called wick-based device, which comprises a reservoir, a wick for absorbing the liquid in the reservoir and transporting it to the emanating body from which the active liquid evaporates.
The main problem of such wick-based devices is the difficulty to achieve a controlled release in the surroundings of the active liquid in order to avoid that the evaporation of the active liquid is too quick or too slow, and the control of a linear delivery, with the same olfactive quality over time, of the fragrance into the surroundings. Moreover, when used to impart a fragrance to a particular room, in combination with a heating element for example, the lack of control can lead to too much or too little fragrance dispensed into the room such that the fragrance is either not perceived or is too strong.
The various wick-based devices disclosed in the prior art can be divided in several categories. Each category is characterized by the fact that the device achieves a controlled release by:    i) the use of special films or occluding systems which enwrap the emanating body;    ii) the use of a cover to regulate, over the lifetime of the device, the surface of the emanating body from which the active liquid can evaporate (i.e., the evaporative surface); or    iii) the use of an electrically powered assistance such as heating or a fan.
These devices are complex to realize and require additional elements. Moreover, with the exception of the electrically assisted devices, the other devices require, in general, the use of an aqueous solution or emulsion of the active liquid, thus implying the use of large amounts of liquid and of surfactants which may be detrimental to the effective releasing performance of the device.
To try to resolve these problems, U.S. Pat. No. 7,441,755 discloses a non-electrically powered device comprising: a) a reservoir chamber having an open end; b) a non-aqueous active volatile liquid composition containing at least two ingredients; c) a reservoir chamber lid securely covering the open end of the reservoir chamber, the lid having at least one aperture; and d) a wick-emanator superstructure securely positioned in the aperture of the reservoir chamber lid. The superstructure includes I) an emitting part extending over the reservoir chamber lid and having an evaporative surface exposed to the surrounding air; and II) a wicking part extending down through the lid and in submerged contact with the active volatile liquid. This device is characterized in that i) at least 60% by weight of the non-aqueous active volatile liquid composition comprising ingredients having a vapor pressure of between 4 Pa and 270 Pa; ii) the emitting part has a weight of between 80 and 1000 grams per square meter of evaporative surface and an absorbency of between 0.01 and 0.1 grams of non-aqueous active volatile liquid composition per square centimeter of evaporative surface; and iii) less than about 20% by weight of the non-aqueous active volatile liquid composition is absorbed by the emitting part. This certainly increases the evaporative surface area, but is reliant upon the surrounding air to disperse the evaporated liquid.
U.S. Pat. No. 7,499,632 discloses a distribution device for distributing volatile fluids in air. In an exemplary embodiment, the distribution device includes a wick formed of a solid material which is impregnated with a volatile fluid, such as a scented liquid, a disinfectant, a fungicide, an anti-allergenic substance, an insect repellant, or an insecticide, for example. In another embodiment, the device includes a substantially hollow, tubular shaped wick which includes a portion that is exposed to the surrounding environment and a portion that is in liquid communication with a liquid reservoir containing a volatile fluid. The wick is positioned in the liquid reservoir and in a close fitting engagement with an open end of the liquid reservoir. The hollow configuration of the wick provides a greater exposed surface area to enhance the evaporation of the liquid into the surrounding environment. Even so, the resulting area, is relatively small such that the types of liquid that are suitable for us are those that are highly volatile. This limits that type and range of fragrances that can be dispensed by the device.
Accordingly, there remains a need in the art for improvements in this area. And these are now provided by the present invention.